Your statement contradicts itself. As you say, you can make it to the finals losing more then you win, so why would you then say making a Grand Final is the guage for success. You can lose more then you win and string 3 wins together and make the final. Does that make you more successful then a team who wins 15 games but loses a semi final?
Success for each club is different. Clubs with their own Cup teams have a huge advantage in recruitment. They should all be aiming for top 4 minimum, like Wenty, Mounties and Wests all are and Blacktown have no excuse not to be. Clubs like Brothers and Guildford have no feeders and different budgets to say a Mounties, St.Marys, Cabra and Wenty so success for them is different again. Teams with strong ISP clubs and u20s clubs such as Penrith will always do well as well as they get quality players handed to them. Would you rather get players from Norths who have not won a game yet or Penrith u20s where some end up NRL players eventually. Logistics also play a major part. 80% or more of the competition are from out west so teams there have a huge advantage. Teams who have strong ISP affiliations will always have an advantage. Look at Glebe/Burwood last year who had lots of Newtown and were one minute from a Grand Final. This year they have had less help and are struggling. Different things play a part and all clubs are in different situations and judge success differently. Coaches should be judged the same way and are all in different situations. Asquith really have no right to be where they are on the table when you consider logistics, budget, feeder arrangement with Norths who take their best players and give back worse or none at all. They are in their 2nd year back in Ron Massey and are punching above their weight. People always want to cut a club or coach down when they start doing ok.
As for why he hasn't been at a big club. Youd have to ask them but generally most jobs go to people who know someone at the club already. Footy will always be a jobs for the boys industry.